Thermodynamic Property of B in Molten Si and Phase Relations in the Si–Al–B System

Abstract

The thermodynamic property of B in molten Si, which is of importance for optimizing or designing the B removal process from Si, was determined as the following equation by equilibrating molten Si with Si₃N₄ and BN at 1693 and 1773 K. lnγ^°_B(l)in molten Si=1.19(±0.25)+\\frac289(±450)T (1693–1923 K) Also, the standard Gibbs energy change for N₂ dissolution into molten Si was determined as the following equation. & \\frac12N₂(g)=N(mass%, in molten Si)
& ΔG^°=-36,200(±23,500)+39.8(±13.6)T  (J/mol) (1693–1773 K) On the other hand, to understand the B behavior in the solidification refining of Si with Si–Al melt, phase relations in the Si–Al–B system were investigated at 1373–1573 K. The boride in equilibrium with Si–Al melt was clarified as AlB₁₂ solid solution and the thermodynamic property of that solid solution was discussed.